Microfluidic devices and systems have been gaining increasing interest for their ability to provide improved methods of performing chemical, biochemical and biological analysis and synthesis. In particular, the small size and automatability of these microfluidic systems provides a variety of advantages in terms of low reagent requirements, low space requirements, shorter reaction times, and integratability. All of these advantages together, provide systems which can be extremely useful in performing large numbers of reactions in parallel, in order to provide enhanced analytical throughput.
In general, the production of microfluidic devices has been enabled by advancements in microfabrication technology used in the electronics and semiconductor manufacturing industries. Specifically, technologies, such as photolithography, wet chemical etching, injection molding of plastics, and the like, have been used to fabricate microscale channels and wells in the surface of planar substrates. Overlaying a second planar substrate on the surface of the first creates the microfluidic channels and chambers of the device. While these microfabrication techniques permit the incorporation of relatively complex channel networks in a relatively small area, the ability to further reduce the size of microfluidic devices produced in this manner has been somewhat limited by the two dimensional orientation of the channel networks. Specifically, because channel networks have been generally defined in two dimensions, e.g., in a single layer, different channel networks could not cross or otherwise occupy the same area on the substrate.
In order to allow further reduction of microfluidic device size, it would therefore be desirable to provide microfluidic devices that are not limited by the two-dimensional nature of typical microfluidic devices. The present invention meets these and other needs.